On 23 July 1947, the Norwegian cargo vessel Ocean Liberty arrived in Brest (Brittany) after crossing the Atlantic. 5 days later, a port worker noticed smoke coming from one of the holds which had not been opened as its contents, ammonium nitrate, were bound for Le Havre and Boulogne. The worker, remembering the Grandcamp disaster which had occurred three months earlier in Texas City, warned the captain, the fire brigade, the port authority and the Marines.

A major and potentially very dangerous fire indeed then broke out onboard the Ocean Liberty and spread rapidly due to the east wind. A towing attempt was made but the vessel grounded on shoals near the port. While the team attempted to scuttle the vessel, still in the clutches of flames, to put out the fire, the cargo exploded. The shock wave spread throughout the Bay of Brest. The Ocean Liberty disintegrated and disappeared almost completely, and a cloud of smoke developed above where the explosion had occurred, extending over 4 km in altitude. All the windows in the city and its surrounding area shattered into pieces. As in Texas City, a tidal wave caused by the explosion swept along the coast and sparked panic among bathers. In total, 22 people were killed in this accident, 4 went missing and hundreds were injured.

On 15 December 1954, the civil court of Brest upheld the liability of the American ammonium nitrate manufacturer. The court of appeal of Rennes confirmed the judgement in 1957, on the grounds that in 1947 it was not scientifically known that ammonium nitrate was dangerous in itself, that it heated and that it was at risk of igniting and causing an explosion.